Write head design and method for reducing adjacent track interference at very narrow track widths

ABSTRACT

A perpendicular write head having a wrap around trailing shield for reducing stray field writing and adjacent track interference. A method for constructing such a write head allows for excellent control of side shield gap thickness and trailing shield gap thickness, and allows the ratio of side gap to trailing gap thicknesses to be maintained at about two to one as desired. The method includes depositing forming a write pole by constructing a mask which may include a bi-layer hard mask, and then ion milling to form the write pole. Once the write pole has been formed, a layer of alumina or some other non-magnetic material can be conformally deposited. A reactive ion mill (RIM) can be performed to open up the top of the write pole (remove the horizontally disposed portions of the alumina layer). Then, a second layer of alumina or some other non-magnetic material can be deposited, and the write pole can be plated. The thickness of the side shield gaps is defined by the sum of the final thicknesses of the first and second alumina layers, while the thickness of the first magnetic layer defines the thickness of the trailing shield gap.

FIELD OF THE INVENTION

The present invention relates to perpendicular magnetic recording andmore particularly to a novel trailing magnetic shield design and amethod for manufacturing such a shield design.

BACKGROUND OF THE INVENTION

The heart of a computer's long term memory is an assembly that isreferred to as a magnetic disk drive. The magnetic disk drive includes arotating magnetic disk, write and read heads that are suspended by asuspension arm adjacent to a surface of the rotating magnetic disk andan actuator that swings the suspension arm to place the read and writeheads over selected circular tracks on the rotating disk. The read andwrite heads are directly located on a slider that has an air bearingsurface (ABS). The suspension arm biases the slider toward the surfaceof the disk, and when the disk rotates, air adjacent to the disk movesalong with the surface of the disk. The slider flies over the surface ofthe disk on a cushion of this moving air. When the slider rides on theair bearing, the write and read heads are employed for writing magnetictransitions to and reading magnetic transitions from the rotating disk.The read and write heads are connected to processing circuitry thatoperates according to a computer program to implement the writing andreading functions.

The write head traditionally includes a coil layer embedded in first,second and third insulation layers (insulation stack), the insulationstack being sandwiched between first and second pole piece layers. A gapis formed between the first and second pole piece layers by a gap layerat an air bearing surface (ABS) of the write head and the pole piecelayers are connected at a back gap. Current conducted to the coil layerinduces a magnetic flux in the pole pieces which causes a magnetic fieldto fringe out at a write gap at the ABS for the purpose of writing theaforementioned magnetic transitions in tracks on the moving media, suchas in circular tracks on the aforementioned rotating disk.

In recent read head designs a spin valve sensor, also referred to as agiant magnetoresistive (GMR) sensor, has been employed for sensingmagnetic fields from the rotating magnetic disk. The sensor includes anonmagnetic conductive layer, hereinafter referred to as a spacer layer,sandwiched between first and second ferromagnetic layers, hereinafterreferred to as a pinned layer and a free layer. First and second leadsare connected to the spin valve sensor for conducting a sense currenttherethrough. The magnetization of the pinned layer is pinnedperpendicular to the air bearing surface (ABS) and the magnetic momentof the free layer is located parallel to the ABS, but free to rotate inresponse to external magnetic fields. The magnetization of the pinnedlayer is typically pinned by exchange coupling with an antiferromagneticlayer.

The thickness of the spacer layer is chosen to be less than the meanfree path of conduction electrons through the sensor. With thisarrangement, a portion of the conduction electrons is scattered by theinterfaces of the spacer layer with each of the pinned and free layers.When the magnetizations of the pinned and free layers are parallel withrespect to one another, scattering is minimal and when themagnetizations of the pinned and free layer are antiparallel, scatteringis maximized. Changes in scattering alter the resistance of the spinvalve sensor in proportion to cos θ, where θ is the angle between themagnetizations of the pinned and free layers. In a read mode theresistance of the spin valve sensor changes proportionally to themagnitudes of the magnetic fields from the rotating disk. When a sensecurrent is conducted through the spin valve sensor, resistance changescause potential changes that are detected and processed as playbacksignals.

When a spin valve sensor employs a single pinned layer it is referred toas a simple spin valve. When a spin valve employs an antiparallel (AP)pinned layer it is referred to as an AP pinned spin valve. An AP spinvalve includes first and second magnetic layers separated by a thinnon-magnetic coupling layer such as Ru. The thickness of the spacerlayer is chosen so as to be antiparallel coupled to the magnetizationsof the ferromagnetic layers of the pinned layer. A spin valve is alsoknown as a top or bottom spin valve depending upon whether the pinninglayer is at the top (formed after the free layer) or at the bottom(before the free layer).

The spin valve sensor is located between first and second nonmagneticelectrically insulating read gap layers and the first and second readgap layers are located between ferromagnetic first and second shieldlayers. In a merged magnetic head a single ferromagnetic layer functionsas the second shield layer of the read head and as the first pole piecelayer of the write head. In a piggyback head the second shield layer andthe first pole piece layer are separate layers.

Magnetization of the pinned layer is usually fixed by exchange couplingone of the ferromagnetic layers (AP1) with a layer of antiferromagneticmaterial such as PtMn. While an antiferromagnetic (AFM) material such asPtMn does not in and of itself have a magnetization, when exchangecoupled with a magnetic material, it can strongly pin the magnetizationof the ferromagnetic layer.

In order to meet the ever increasing demand for improved data rate anddata capacity, researchers have recently been focusing their efforts onthe development of perpendicular recording systems. A traditionallongitudinal recording system, such as one that incorporates the writehead described above, stores data as magnetic bits orientedlongitudinally along a track in the plane of the surface of the magneticdisk. This longitudinal data bit is recorded by a fringing field thatforms between the pair of magnetic poles separated by a write gap.

A perpendicular recording system, by contrast, records data asmagnetization oriented perpendicular to the plane of the magnetic disk.The magnetic disk has a magnetically soft underlayer covered by a thinmagnetically hard top layer. The perpendicular write head has a writepole with a very small cross section and a return pole having a muchlarger cross section. A strong, highly concentrated magnetic field emitsfrom the write pole in a direction perpendicular to the magnetic disksurface, magnetizing the magnetically hard top layer. The resultingmagnetic flux then travels through the soft underlayer, returning to thereturn pole where it is sufficiently spread out and weak that it willnot erase the signal recorded by the write pole when it passes backthrough the magnetically hard top layer on its way back to the returnpole.

One of the features of perpendicular recording systems is that the highcoercivity top layer of the magnetic medium has a high switching field.This means that a strong magnetic field is needed to switch the magneticmoment of the medium when writing a magnetic bit of data. In order todecrease the switching field and increase recording speed, attempts havebeen made to angle or “cant” the write field being emitted from thewrite pole. Canting the write field at an angle relative to the normalof the medium makes the magnetic moment of the medium easier to switchby reducing the switching field. Modeling has shown that a single polewriter in a perpendicular recording system can exhibit improvedtransition sharpness (ie. better field gradient and resolution), achievebetter media signal to noise ratio, and permit higher coercive fieldmedia for higher areal density magnetic recording if, according to theStoner-Wohlfarth model for a single particle, the effective flux fieldis angled. A method that has been investigated to cant the magneticfield has been to provide a trailing magnetic shield adjacent to thewrite head, to magnetically attract the field from the write pole.

The trailing shield can be a floating design, in that the magnetictrailing shield is not directly, magnetically connected with the otherstructures of the write head. Magnetic field from the write pole resultsin a flux in the shield that essentially travels through the magneticmedium back to the return pole of the write head. Various dimensions ofthe shield are critical for the floating trailing shield to operatecorrectly. For instance, effective angling or canting of the effectiveflux field is optimized when the write pole to trailing shieldseparation (gap) is about equal to the head to soft underlayer spacing(HUS) and the trailing shield throat height is roughly equal to half thetrack-width of the write pole. This design improves write field gradientat the expense of effective flux field. To minimize effective flux fieldlost to the trailing shield and still achieve the desired effect, thegap and shield thickness are adjusted to minimize saturation at theshield and effective flux field lost to the shield respectively. Inorder for a trailing shield to function optimally, the thickness of thetrailing shield gap must be tightly controlled. Therefore, there is aneed for a means for accurately controlling such trailing gap thicknessduring manufacture.

A problem that arises as a result of shrinking trackwidth designs,whether they be longitudinal recording systems or perpendicularrecording systems, is that the tracks are so close to one another thatthe signal from a write head can inadvertently write to an adjacenttrack. This has been referred to as adjacent track interference, andbecomes more of a problem as designers attempt to fit more tracks ofdata into a given area of disk space.

Therefore, there is a need for a method or design that can produce awrite head that will not cause adjacent track interference, even atextremely high track densities. Such a design or method must bemanufacturable, allowing in large batch manufacturing processes, withoutincurring significant additional manufacturing expense or complexity.

SUMMARY OF THE INVENTION

The present invention provides a magnetic write head having a wraparound trailing magnetic shield for use in a perpendicular magneticrecording system. The invention includes a magnetic write pole having atrailing edge, a leading edge and first and second laterally opposedsides. The shield has a trailing portion that extends in the trailingdirection from the trailing edge of the write pole and is separated fromthe trailing edge of the write pole by a trailing shield gap. The shieldalso has side shield portions that extend laterally from the sides ofthe write pole and are separated from the write pole by a side shieldgap. The side shield gap preferably has a thickness of about 1.5 to 2.5times the trailing gap thickness.

A magnetic write head according to an embodiment of the invention can beconstructed by a method that includes providing a substrate such as analumina layer or some other material. A layer of write pole material isdeposited over the substrate, and a mask structure is formed over thewrite pole material. The mask structure may include a hard mask, a imagetransfer layer formed over the hard mask and a photosensitive layer suchas photoresist formed over the image transfer layer. The hard mask layercan be, for example a single layer or can be multiple layers, such as alayer of alumina and a layer of diamond like carbon (DLC) formed overthe alumina layer. The image transfer layer can be, for exampleDURAMIDE® or some similar material.

The photosensitive material can be photolithographically patterned anddeveloped to form a photo mask having a desired width and shape. Areactive ion etch (RIE) can be performed to transfer the image of thephoto layer into the image transfer layer and possibly into all or aportion of the hard mask layer (such as into the DLC layer). A reactiveion mill can be performed to transfer the image of the photo mask, imagetransfer layer and DLC layer into the underlying alumina layer.

An ion mill can then be performed to remove portions of the write polematerial not covered by the overlying mask structure. The ion mill canbe performed at an angle with respect to normal to form the write polewith a desired trapezoidal configuration.

A first layer of non-magnetic gap material, such as alumina, can then bedeposited. A reactive ion mill (RIM) can then be performed to removehorizontally disposed portions of the first non-magnetic write gapmaterial, such as from the top (trailing edge) of the write pole. Thisleaves vertical walls formed on at the first and second sides of thewrite pole. These walls formed at the sides of the write pole extendbeyond above the top (trailing edge) of the write pole. In other words,the walls extend in the trailing direction beyond the trailing edge ofthe write pole.

A second layer of non-magnetic gap material can then be deposited. Thesecond layer of gap material covers the trailing edge of the write poleand also over the sides of the wall formed by the first layer of gapmaterial. The first and second non-magnetic gap layers can be depositedby a conformal deposition method, such as chemical vapor deposition(CVD) or atomic layer deposition (ALD). Then, a magnetic shield can bedeposited. The magnetic shield can be deposited, by first sputterdepositing an electrically conductive material such as Rh, and thenelectroplating a magnetic material such as NiFe.

These and other features and advantages of the invention will beapparent upon reading of the following detailed description of preferredembodiments taken in conjunction with the Figures in which likereference numerals indicate like elements throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of thisinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings which are not to scale.

FIG. 1 is a schematic illustration of a disk drive system in which theinvention might be embodied;

FIG. 2 is an ABS view of a slider, taken from line 2-2 of FIG. 1,illustrating the location of a magnetic head thereon;

FIG. 3 is a cross sectional view view, taken from line 3-3 of FIG. 2 androtated 90 degrees counterclockwise, of a magnetic head according to anembodiment of the present invention;

FIG. 4A is an ABS view of the write head taken from line 4-4 of FIG. 3;

FIG. 4B is an ABS view taken from circle 4B of FIG. 4A;

FIGS. 5-13 are ABS views similar to that of FIGS. 4A and 4B, showing amagnetic head in various intermediate stages of manufacture andillustrating a method of manufacturing a magnetic head according to anembodiment of the invention;

FIGS. 14-23 are ABS views of an magnetic write head in variousintermediate stages of manufacture illustrating an alternate method ofconstructing a magnetic write head according to an embodiment of theinvention;

FIGS. 24 and 25 are flow charts illustrating methods of manufacturing amagnetic write head;

FIG. 26 is an ABS view of a longitudinal write head according to anembodiment of the invention;

FIG. 27 is a cross sectional view, taken from line 27-27 of FIG. 26, ofa longitudinal write head according to an embodiment of the invention;

FIG. 28 is an ABS view of a prior art longitudinal write head;

FIGS. 29-36 are ABS views of a longitudinal write head in variousintermediate stages of manufacture illustrating a method ofmanufacturing a write head according to an embodiment of the invention;and

FIG. 37 is a flowchart illustrating a method of manufacturing a writehead according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is of the best embodiments presentlycontemplated for carrying out this invention. This description is madefor the purpose of illustrating the general principles of this inventionand is not meant to limit the inventive concepts claimed herein.

Referring now to FIG. 1, there is shown a disk drive 100 embodying thisinvention. As shown in FIG. 1, at least one rotatable magnetic disk 112is supported on a spindle 114 and rotated by a disk drive motor 118. Themagnetic recording on each disk is in the form of annular patterns ofconcentric data tracks (not shown) on the magnetic disk 112.

At least one slider 113 is positioned near the magnetic disk 112, eachslider 113 supporting one or more magnetic head assemblies 221. As themagnetic disk rotates, slider 113 moves radially in and out over thedisk surface 122 so that the magnetic head assembly 121 may accessdifferent tracks of the magnetic disk where desired data are written.Each slider 113 is attached to an actuator arm 119 by way of asuspension 115. The suspension 115 provides a slight spring force whichbiases slider 113 against the disk surface 122. Each actuator arm 119 isattached to an actuator means 127. The actuator means 127 as shown inFIG. 1 may be a voice coil motor (VCM). The VCM comprises a coil movablewithin a fixed magnetic field, the direction and speed of the coilmovements being controlled by the motor current signals supplied bycontroller 129.

During operation of the disk storage system, the rotation of themagnetic disk 112 generates an air bearing between the slider 113 andthe disk surface 122 which exerts an upward force or lift on the slider.The air bearing thus counter-balances the slight spring force ofsuspension 115 and supports slider 113 off and slightly above the disksurface by a small, substantially constant spacing during normaloperation.

The various components of the disk storage system are controlled inoperation by control signals generated by control unit 129, such asaccess control signals and internal clock signals. Typically, thecontrol unit 129 comprises logic control circuits, storage means and amicroprocessor. The control unit 129 generates control signals tocontrol various system operations such as drive motor control signals online 123 and head position and seek control signals on line 128. Thecontrol signals on line 128 provide the desired current profiles tooptimally move and position slider 113 to the desired data track on disk112. Write and read signals are communicated to and from write and readheads 121 by way of recording channel 125.

With reference to FIG. 2, the orientation of the magnetic head 121 in aslider 113 can be seen in more detail. FIG. 2 is an ABS view of theslider 113, and as can be seen the magnetic head including an inductivewrite head and a read sensor, is located at a trailing edge of theslider. The above description of a typical magnetic disk storage system,and the accompanying illustration of FIG. 1 are for representationpurposes only. It should be apparent that disk storage systems maycontain a large number of disks and actuators, and each actuator maysupport a number of sliders.

With reference now to FIG. 3, the magnetic head 221 for use in aperpendicular magnetic recording system is described. The head 221includes a write element 302 and a read sensor 304. The read sensor ispreferably a giant magnetoresistive (GMR) sensor and is preferably acurrent perpendicular to plane (CPP) GMR sensor. CPP GMR sensors areparticularly well suited for use in perpendicular recording systems.However, the sensor 304 could be another type of sensor such as acurrent in plane (CIP) GMR sensor or, a tunnel junction sensor (TMR) orsome other type of sensor. The sensor 304 is located between andinsulated from first and second magnetic shields 306, 308 and embeddedin a dielectric material 307. The magnetic shields, which can beconstructed of for example CoFe or NiFe, absorb magnetic fields, such asthose from uptrack or down track data signals, ensuring that the readsensor 304 only detects the desired data track located between theshields 306, 308. A non-magnetic, electrically insulating gap layer 309may be provided between the shield 308 and the write head 302.

With continued reference to FIG. 3, the write element 302 includes awrite pole 310 that is magnetically connected with a magnetic shapinglayer 312, and is embedded within an insulation material 311. The writepole has a small cross section at the air bearing surface and isconstructed of a material having a high saturation moment, such as NiFeor CoFe. The shaping layer 312 is constructed of a magnetic materialsuch as CoFe or NiFe and has a cross section parallel to the ABS surfacethat is significantly larger than that of the write pole 310.

The write element 302 also has a return pole 314 that preferably has asurface exposed at the ABS and has a cross section parallel with the ABSsurface that is much larger than that of the write pole 310. The returnpole 314 is magnetically connected with the shaping layer 312 by a backgap portion 316. The return pole 314 and back gap 316 can be constructedof, for example, NiFe, CoFe or some other magnetic material.

An electrically conductive write coil 317, shown in cross section inFIG. 3, passes through the write element 302 between the shaping layer312, and the return pole 314. The write coil 317 is surrounded by anelectrically insulating material 320 that electrically insulates theturns of the coil 317 from one another and electrically isolates thecoil 317 from the surrounding magnetic structures 310, 312, 316, 314.When a current passes through the coil 317, the resulting magnetic fieldcauses a magnetic flux to flow through the return pole 314, back gap316, shaping layer 312 and write pole 310. This magnetic flux causes awrite field 321 to be emitted toward an adjacent magnetic medium. Theshaping layer 312 is also surrounded by an insulation layer 321 whichseparates the shaping layer 312 from the ABS. The insulation layers 320,321, 311 can all be constructed of the same material, such as alumina(Al₂0₃) or of different electrically insulating materials.

The write head element 302 also includes a trailing shield 322. Withreference to FIG. 4A, the trailing shield 322 wraps around the writepole 310 to provide side shielding as well as trailing shielding fromstray magnetic fields. These stray magnetic fields can be from theportions of the write head 302 itself, or could also be from adjacenttrack signals or from magnetic fields from external sources.

With reference now to FIG. 4B the configuration of the write pole 310and the surrounding portions of the trailing shield 322 are shownenlarged and in greater detail. The write pole 310 has a trailing edge402 and a leading edge 404. The terms trailing and leading are withrespect to the direction of travel along a data track during when thewrite head 302 is in use. The write pole 310 also preferably has firstand second laterally opposing sides 406, 408 that are configured todefine a width at the leading edge 404 that is narrower than the widthat the trailing edge 404, forming a write pole 310 having a trapezoidalshape. This trapezoidal shape is useful in preventing adjacent trackwriting due to skew of the write head 302 when the head 302 is locatedat extreme outer or inner positions over the disk, however, thistrapezoidal shape of the write head 310 is not necessary to practice thepresent invention.

With continued reference to FIG. 4B, the magnetic trailing shield 322 isseparated from each side 406, 408 of the write pole 310 by a side gap410. The trailing shield 322 is also separated from the trailing shield,by a trailing gap 412. The thickness of each of the side gaps 410 ispreferably about 1.5 to 2.5 or about 2 times the thickness of thetrailing gap 412. The materials defining and filling the side andtrailing gaps 410, 412 are preferably non-magnetic materials and may bethe same materials or may be different materials. Preferably, the sidegaps include a first non-magnetic layer 414, which may be for examplealumina, and a second non-magnetic layer 416 which may also be aluminaor some other material. The second non-magnetic layer 416 alsopreferably extends over the top of the write pole 310 to define thetrailing gap 412.

As can be seen with reference to FIG. 4B, the trailing shield 322 can beconfigured with notches 418 at either side of the write pole 310. Thenotches can be described as extensions of the side gaps 410 that extendin the trailing direction slightly beyond the trailing edge gap 412. Thenotches 418 are an artifact of a process for constructing the trailingshield 322 by a process that will be described below. The trailingshield 322 can be constructed of a magnetic material such as NiFe.

With reference now to FIGS. 5 through 13, a method for constructing awrite pole and a wrap around trailing shield according to an embodimentis described. With particular reference to FIG. 5, a substrate layer 502is provided. The substrate 502 can include, for example, the insulationlayer 321 and shaping layer 312 described with reference to FIGS. 3 and4. In that case, the shaping layer 312 can be constructed of, forexample NiFe, which has been plated into a photoresist frame. Theinsulation layer 321 could be constructed by filling with a materialsuch as alumina after the shaping layer has been defined and itsphotoresist frame has been lifted off. The alumina layer 321 and shapinglayer 312 can then be planarized by chemical mechanical polishing toprovide a smooth planar surface on which to deposit subsequent layers.The formation of the substrate 502 (shaping layer 312, and insulation321 from FIGS. 3 and 4) will be familiar to those skilled in the art andis not illustrated in FIG. 5.

With continued reference to FIG. 5, write pole material 504 is depositedover the substrate 502. The write pole material 504 can be a singlelayer of a suitable high magnetic permeability material such as CoFe, ormore preferably can include many laminations of layers of a highpermeability, low coercivity materials such as CoFe separated by verythin lamination layers, such as thin layers of alumina. The write polematerial 504, whether formed as a single layer or lamination of multiplelayers can be deposited by sputter deposition.

With the write pole material 504 deposited. A series of mask layers 506can be deposited. The mask layers 506 can include a layer of hard maskmaterial 507, which may include a layer of alumina 508 and a layer ofdiamond like carbon (DLC) 510. The hard mask may include only a singlelayer, such as a single layer of alumina or a single layer of DLC, butimproved critical dimension control of the write pole width can beachieved by using a bi-layer hard mask constructed of both alumina andDLC. The mask layers 506 also include an image transfer layer 512constructed of a material such as DURIMIDE®, and a photosensitive maskmaterial 514 such as photoresist. The hard mask layers 507, includingboth the alumina layer 508 and DLC layer 510 can be deposited by sputterdeposition. The image transfer layer 512 and photosensitive layer 514can be deposited (spun onto the wafer).

The photoresist mask 514 is photolithographically patterned to form amask having a desired width for determining a width of the finishedwrite pole 510 (FIGS. 4A, 4B). With reference to FIG. 6, a reactive ionetch (RIE) 602 is performed to transfer the image of the photoresistlayer 514 onto the underlying mask layers 510, 512. The photoresistlayer 514 may be completely consumed by the RIE so that no photoresistlayer 514 actually remains after performing this RIE 602. The RIE 602removes portions of the DLC layer 510 and image transfer layer 512 thatextended beyond the sides of the photoresist layer 514 as shown in FIG.5. However, most of the hard mask layer 508 remains after performing theRIE.

With reference to FIG. 7, a reactive ion milling (RIM) process 702 isperformed to remove portions of the hard mask 508 that are not protectedby the remaining mask layers 510, 512. Then, with reference to FIG. 8,an ion mill 802 is performed to remove write pole material 504 to formthe write pole 510 describe previously with reference to FIGS. 3, 4A and4B. The ion mill 802 is preferably performed at an angle 804 withrespect to a normal to the surfaces of the layers 502-512. This angledion milling removes write pole material 504 in such a manner as to formangled sides on the write pole 310, resulting in a write pole 310 havingthe desired trapezoidal shape discussed previously. The ion mill ispreferably performed sufficiently to remove write pole material 504 downto a level that is slightly below the level of the bottom of the writepole material 510.

With reference now to FIG. 9, a first non-magnetic layer 902 isdeposited. This layer may be alumina or some other non-magneticmaterial. The first non-magnetic layer 902 is preferably deposited by aconformal deposition technique such as atomic layer deposition (ALD) orsome other conformal deposition process. The first non-magnetic layer902 (first alumina layer) is deposited to such a thickness as isnecessary to define a desired side gap between the sides of the writepole and the finished trailing shield. This will become clearer below.

With reference to FIG. 10, a reactive ion milling process RIM 1002 isperformed. The RIM process is a directional process that preferentiallyremoves horizontally disposed portions of the first non-magnetic layer902. The RIM process 1002 is preferably performed sufficiently to removeall of the horizontally disposed portions of the first non-magneticlayer 902, leaving vertical walls 902 remaining at the sides of thewrite pole. As can be seen the non-magnetic walls 902 extend above thetop (trailing edge) of the write pole 310. The RIM process also removesmost if not all of the image transfer layer (DURAMIDE® layer). Withreference to FIG. 9, it can be seen that the RIM process 1002 opens upthe remaining mask structures 512, 510, 508 above the write pole 310.

With reference now to FIG. 11, a reactive ion etch 1102 is performed toremove the remaining image transfer layer 512, as well as the DLC andalumina layers 508, 510 (FIG. 10) from above the write pole 310. Then,with reference to FIG. 12, a second layer of non-magnetic material 1202such as alumina is deposited, preferably by a conformal depositionprocess such as atomic layer deposition (ALD), chemical vapor deposition(CVD) or some similar process. The second non-magnetic layer 1202 isdeposited to such a thickness that it can define the thickness of thetrailing shield 412. As mentioned above, the first non-magnetic layer902 was deposited to such a thickness to determine the thickness of theside gaps 410 when added to the second magnetic layer 1202. As can beseen in FIG. 12, the side gaps 410 are defined by the sum of thethickness of both the first non-magnetic layer 902 and the secondnon-magnetic layer 1202, both of which may be constructed of alumina.This means that when the first magnetic layer 910 is deposited asdescribed in FIG. 9, its deposited thickness should be such that sum ofthe thicknesses of the layers 902 and 1202 define the desired side gap410. As mentioned above, the thickness of each of the side gaps 410 ispreferably about twice (1.5-2.5 times) that of the trailing shield gap412. This means that the first and second non-magnetic layers 902, 1202may be about the same thickness. For example the thickness of the firstand second non-magnetic layers 902, 1202 may be 60-80 nm or about 70 nm,resulting in side shield gaps 410 having thicknesses of 120-160 nm orabout 140 nm and a trailing shield gap 412 of 60-80 nm or about 70 nm.

With reference to FIG. 13, a thin, electrically conductive seed layer1302 is deposited. A photoresist frame (not shown) can then bephotolithographically patterned and constructed to define the outeredges of the trailing shield. A magnetic material such as NiFe 1304 canthen be electroplated to form the trailing shield 322 as described inFIGS. 3, 4A and 4B.

With reference to FIGS. 14-23 another method for constructing a magneticwrite pole having a wrap around shield is described. With particularreference to FIG. 14, a substrate 1402, such as an alumina fill layer isprovided and a full film layer of write pole material 1404 is depositedover the substrate. A mask structure 1406 is provided over the writepole material 1404. The mask structure 1406 includes a first hard maskstructure 1408 that includes a layer of alumina (Al₂O₃) 1410 and a layerof diamond like carbon (DLC) 1412 formed thereover. The layer of Alumina1410 can be 15 o 25 nm or about 20 nm thick. The DLC layer can also be15 to 25 nm or about 20 nm thick. A first image transfer layerconstructed of, for example, DURIMIDE® 1414 is deposited over the hardmask. This first image transfer layer can have a thickness of, forexample, 1100 to 1300 nm or about 1200 nm. A second hard mask structure1416 can then be deposited over the first DURIMIDE® layer 1414. Thesecond hard mask structure 1416 can be constructed of, for example,silicon dioxide (SiO₂) and can have a thickness of, for example 50 to150 nm or about 100 nm. Then, a second image transfer layer 1418, whichmay also be constructed of DURIMIDE®, can then be deposited over thesecond hard mask layer 1416. The second image transfer layer 1418 mayhave a thickness of 40 to 80 nm or about 60 nm. A layer ofphotosensitive mask material 1420 such as photoresist is then depositedat the top of the mask structure 1406 and is photolithographicallypatterned to have a desired width and shape for defining a write pole.

With reference now to FIG. 15, a combination of reactive ion etch (RIE)1502 and reactive ion milling (RIM) 1504 is performed to transfer theimage of the photosensitive mask layer 1420 onto the underlying masklayers 1410-1418, removing all or a portion of layers 1420 and 1418 inthe process.

With reference to FIG. 16, an ion mill 1602 is performed to remove writepole material 1404 to form the write pole. The ion mill 1602 isperformed at an angle with respect to a normal to the deposited layersin order to form the write pole with the desired trapezoidal shapediscussed earlier.

The presence of the second hard mask layer 1416 (FIG. 14) providesimproved control of write pole critical dimensions, by preservingsufficient mask material during the combination RIE and RIM processes1502, 1504 (FIG. 15) for use in the subsequent ion milling process 1602(FIG. 16). The combination of reactive ion etch (RIE) and reactive ionmilling (RIM) are performed to effectively remove both the DLC layer1412 and the alumina layer 1410.

With reference now to FIG. 17, a TMAH developer etch (tetramethylammonium hydroxide) 1702 is performed to remove the remaining imagetransfer layer 1414. With reference now to FIG. 18, a layer of Rh 1802is deposited, preferably by sputter deposition. The Rh layer 1802 canbe, for example, 25 to 35 nm or about 30 nm. With reference now to FIG.19, a layer of non-magnetic material 1902 such as alumina is depositedover the Rh layer 1802. The alumina layer 1902 is preferably depositedby a conformal deposition method such as atomic layer deposition (ALD),chemical vapor deposition (CVD) etc, and may have a thickness of 60-80nm or about 70 nm.

With reference now to FIG. 20, a reactive ion mill (RIM) is performed topreferentially remove horizontally disposed portions of the aluminalayer 1902, leaving the underlying Rh layer 1802 exposed at the top(trailing edge) of the write pole. Then, with reference to FIG. 21, areactive ion etch (RIE) is performed to remove the exposed portions ofthe Rh layer 1802, and also the DLC layer 1412 from the top of the writepole 1404.

With reference to FIG. 22, an electrically conductive seed such as Rh2202 is deposited. This seed layer 2202 is preferably sputter depositedand has a negligible thickness as compared with the other layers. Withreference now to FIG. 23, a magnetic material 2302, such as NiFe can beelectroplated, using the electrically conductive Rh as a plating seed.This magnetic material 2302 forms a wrap around trailing shield havingwell controlled side gap and trailing gap thicknesses.

As can be seen with reference to FIG. 23, the trailing gap 2304 isdefined by the thickness of remaining alumina layer 1410, whereas theside shield gap 2306 at each side of the write pole 1404 is determinedby the sum of the thicknesses of the alumina layer 1802 and the Rh layer1902. Therefore, the trailing gap thickness 2304 and side gapthicknesses 2306 can be accurately controlled by controlling thethickness of the deposited layers 1410, 1802 and 1902.

At this point, a discussion of the bi-layer hard mask structuredescribed in FIGS. 14 through 16 is warranted. Alumina provides anexcellent hard mask for defining the critical width dimensions of thewrite pole. Another advantage of using alumina as a hard mask is thatTMAH developer (tetramethyl ammonium hydroxide) can be used to lift offfencing resulting from the ion process, without issues related to CMPliftoff processes.

However, in order for the alumina layer alone function effectively as ahard mask and withstand the ion milling, it must be deposited about 75nm thick. This is much thicker than the desired trailing shield gapthickness. One cannot simply reduce the alumina hard mask thickness tothe 20 nm or so needed for the trailing gap, as there would not besufficient hard mask to achieve high bevel angle and critical dimensioncontrol for the write pole. Therefore, the use of alumina alone as thehard mask would require an extra step of removing the alumina and thendepositing another material layer to function as the trailing shieldgap. Using a bi-layer hard mask affords the advantage of using analumina hard mask, while also being able to use the alumina portion ofthe hard mask as a trailing shield gap.

With reference to FIG. 24, a method for constructing a sensor asdescribed back in FIGS. 5 through 13 is summarized as follows. In a step2402 a substrate is provided. The substrate can be a combination of analumina fill layer and a magnetic shaping layer, both forming a smoothcoplanar surface. Then, in a step 2404 a series of mask layers aredeposited. The mask layers can include a hard mask which may be a singlelayer of alumina or some other suitable material or may be a multilayerhard mask such as one that includes a layer of alumina and a layer ofdiamond like carbon (DLC) formed thereover. The other mask layers mayinclude one or more image transfer layers, such as a layer of DURIMIDE®,and a layer of photoresist at the top.

In a step 2406, the photoresist layer at the top of the mask structureis photolithographically patterned, and in step 2408 the image of thephotoresist is transferred to the underlying mask layers. The imagetransfer can be performed by a combination of reactive ion etch (RIE)and reactive ion milling (RIM). Then, in a step 2410 an ion mill isperformed to form the write pole. The ion mill is preferably performedat an angle to create a write pole having a desired trapezoidal shape.In a step 2412 a first shield gap layer material is deposited,preferably by a conformal deposition process. The first gap layer can beconstructed of, for example alumina and can be deposited by a processsuch as, for example atomic layer deposition (ALD), chemical vapordeposition (CVD) or some similar deposition method.

In a step 2414 a reactive ion mill is performed to remove horizontallydisposed portions of the first gap layer, thereby opening up the gaplayer over the write pole and exposing any mask layers still remainingover the write pole. Then, in a step 2416 a reactive ion etch (RIE) isperformed to remove the remaining mask layers from over the top of thewrite pole. In a step 2418 a second gap layer is deposited, also by aconformal deposition process such as ALD or CVD. Like the first gaplayer, the second gap layer can be constructed of alumina or some othermaterial. Then, in a step 2420 an electrically conductive plating seedis deposited. The plating seed can be, for example Rh. Then, in a step2422 the wrap around trailing shield can be formed by electroplating amagnetic material such as NiFe or some other magnetically permeablematerial.

With reference now to FIG. 25, a method for constructing a sensor asdescribed in FIGS. 14-23 can be summarized as follows. First in a step2502 a substrate is provided, this can be for example a combination ofalumina fill and a magnetic shaping layer, both of which have a smoothcoplanar surface. Then, in a step 2504 one or more layers of write polematerial is deposited on the substrate. In a step, 2506 a mask structureis deposited. The mask structure includes a bi-layer hard mask at thebottom of the mask structure, the bi-layer hard mask including a layerof alumina and a layer of DLC formed on the alumina. The mask structurealso includes an image transfer layer, which may have another hard masklayer interposed in a layer of DURIMIDE®. The mask structure alsoincludes a photoresist layer at the top. In a step 2508, the photoresistlayer at the top of the mask structure is photolithographicallypatterned. Then, in a step 2510 a combination of reactive ion etching(RIE) and reactive ion milling (RIM) is performed to transfer the imageof the photoresist layer on the underlying layers of the mask.

In a step 2512 an ion mill is performed to form the write pole. The ionmill is preferably performed at an angle in order to form a desiredtrapezoidal write pole. In a step 2514, any remaining DURIMIDE isstripped using a TMAH etch. Then, in a step 2516, a layer of Rh isdeposited. In a step 2518 a layer of alumina is deposited. Then, in astep 2520 a reactive ion mill (RIM) is performed to open up the Rh layerat the top of the write pole. In a step 2522 another ion mill isperformed to remove the Rh that was exposed in the previous RIM process2520. Then, in a step 2524 an electrically conductive seed layer, suchas Rh is deposited so that the wrap around trailing shield can be platedin a step 2526.

With reference now to FIG. 26 a longitudinal write pole according to anembodiment of the invention is described. FIG. 26 shows a longitudinalwrite head 2602 as viewed from the air bearing surface ABS. The writehead 2602 includes a bottom pole structure 2604 and a top pole structure2606. The bottom pole structure (P1) 2604 may be constructed as a singlemagnetic layer, while the top pole structure 2606 may be constructed asmultiple layers including a P2 pole structure 2608 and a P3 polestructure 2610. An insulator fill material 2612 fills the area aroundthe poles 2604, 2606 as viewed from the ABS.

With reference to FIG. 27, the write head 2602 includes a write coil2614 that passes between the top and bottom poles 2604, 2606. The coil2614 is encased in a non-magnetic, electrically conductive insulationlayer 2616 that may be, for example, alumina. A magnetic back gap layer2618 magnetically connects the top and bottom poles 2604, 2606 at theback of the write head 2602. A layer of write gap material 2620 isformed on the top of a portion of the bottom pole and forms a write gapbetween the top and bottom poles 2604, 2606. The write gap can beconstructed of several non-magnetic materials such as alumina, silicondioxide, etc. When current flows through the coil 2616, a magnetic fieldis generated that flows through the poles 2604, 2606. This field fringesout across the write gap at the ABS causing a fringing field that writesa magnetic bit onto an adjacent magnetic medium (not shown).

The first pole is configured with a notch 2622 that has a steep shoulder2624. The notch may have a substantially vertical portion 2626 that mayextend about 0 to 10 nm from the top of the bottom pole (P1) to thebeginning of the steep shoulder portion 2624. At least a portion of thesteep shoulder portion 2624 preferably forms an angle 2628 of 40-50degrees or about 45 degrees with the planes defined by the depositedlayers. This angle has been found to provide the best balance betweenavoiding stray magnetic fields and preventing pole tip saturation, aswill be explained further below.

This steep shouldered notch 2622 advantageously prevents stray fieldsfrom occurring while also preventing saturation of the pole tip. Strayfields create a problem, because they can lead to adjacent trackinterference. Without the steep shouldered notched structure 2622 shownparticularly in FIG. 26, magnetic fields extending between the P2 layer2608 and the P1 layer 2604 would tend to extend outward to the sides ofthe P1 layer.

Such a disadvantageous side extending magnetic field can be seen withreference to FIG. 28, which shows an ABS view of a prior art write headconfigured without the steep shouldered notch of the present invention.As can be seen, the prior art pole structure has a bottom pole 2802 anda top pole 2804 with a notch 2806 formed in the bottom pole that extendsstraight down and then terminates at an essentially horizontal orslightly sloping surface 2808. A non-magnetic write gap 2803 is formedbetween the top and bottom poles 2802, 2804.

As magnetic field extends between the top and bottom pole 2802, 2804, asignificant portion of the field 2810 extends outward beyond the sidesof the intended write width, the field being attracted to the horizontalportion of the bottom pole 2802. Merely increasing the depth of thenotch 2806 a substantial amount downward would prevent side writing, butwould also lead to magnetic saturation of the pole tip and would,therefore, result in substantially decreased magnetic performance of thewrite head. Therefore, there is a need for a write head design that canprevent such side reading, while also avoiding magnetic saturation ofthe write pole tip. The present invention, an embodiment of which isdescribed in FIGS. 26 and 27, solves this problem by providing such awrite head design.

With reference again to FIG. 29-36, a method of constructing a writepole having a steep shoulder notch according to the present invention isdescribed. With particular reference to FIG. 29, a substrate 2902 suchas an alumina layer or some other non-magnetic layer is provided. Afirst layer of magnetic material 2904 is then deposited to provide thelower magnetic pole P1 2604 described with reference to FIGS. 26 and 27.The first magnetic layer can be a magnetic material such as NiFe or someother suitable material. A write gap material 2906 is deposited over theP1 layer. The write gap material can be, for example alumina or someother non-magnetic material. An electrically conductive seed layer 2908is then formed over the write gap layer 2906 to provide an electricallyconductive surface on which to subsequently electroplate the P2 pole aswill be described below. The seed layer can be formed of variousmaterials and is preferably constructed of the material that will makeup the P2 pole, such as NiFe or CoFe.

With continued reference to FIG. 29 a mask structure 2909 formed overthe P2 seed layer 2908 includes a layer of material that is removable byreactive ion etching (RIEable film) 2910. The RIEable film 2910 can be,for example, SiO₂, SiN, Si, Ta, Ta₂O₅, DLC Tungsten, DURIMIDE®, etc, andcan be deposited to a thickness of about 80 nm. A layer ofPolymethylglutarimide (PMGI film) 2912, or some similar material, isdeposited over the RIEable film layer 2910. The PMGI layer can bedeposited to a thickness of about 60 nm. A deep UV photoresist layer2914 is deposited over the PMGI layer. The photoresist layer 2914 can bedeposited by spinning it onto the wafer as a film. Because it is a deepUV photoresist, the layer 2914 can be deposited relatively thick, suchas about 4 um.

With reference to FIG. 30, the photoresist layer can bephotolithographically patterned by a deep ultraviolet (deep UV)photolithography to form a trench 3002 having desired dimensions forforming a P2 pole piece. The process of exposing and developing thephotoresist layer 2914 not only results in the trench 3002, but alsoforms an undercut 3004 in the PMGI layer 2912. The undercut 3004 mayextend about 0.1 to 0.2 um laterally outward beyond the edges of thetrench 3002 formed in the photoresist layer 2914.

With reference now to FIG. 31, a reactive ion etch (RIE) 3102 isperformed to remove portions of the RIEable layer 2910 that are exposedby the trench 3002 formed in the photoresist layer 2014. As can be seenin FIG. 31, the removed portion of RIEable film 2910 has a width that isslightly larger than the width of the trench 3002, but that issignificantly smaller than the outermost portions of the undercuts 3004.

With reference now to FIG. 32, a magnetic material 3202 such as NiFe orCoFe is electroplated into the trench 3002, with the magnetic material3202 extending into the undercuts 3004.

The deep UV photoresist 2914 and PMGI can be stripped off, such as by achemical liftoff process, resulting in the structure shown in FIG. 33.As can be seen, the magnetic material that was deposited in to theundercuts 3004 (FIG. 32) forms laterally extending P2 wings 3302 nearthe bottom of the P2 pole structure formed by the magnetic material3202. These wings may extend 0.1 to 0.2 um or some dimension greaterthan 0.1 um from the sides of the P2 pole structure 3202.

With reference now to FIG. 34, a reactive ion etch (RIE) 3402 isperformed. P2 wings 3302 form a RIE hard mask that protects portions ofthe RIEable film 2910 from removal during the RIE 3402. The structureresulting from the P2 wings 3302 and remaining RIEable layer 2910results in steep shoulder pedestal structure, having ion mill resistantwings 3404 having a thickness (measured vertically in FIG. 34)preferably greater than 0.1 um.

With reference now to FIG. 35, an ion mill 3502 is performed,sufficiently to remove the P2 seed layer, and the gap layer. As can beseen, the write gap layer and the bottom of the P2 pole 3202 extendlaterally outward to form wings or steps 3504. Then, with reference toFIG. 36, the ion mill 3502 continues to remove underlying P1 first polematerial 2904. The ion mill 3502 may include a combination of millingstraight down to remove P1 material 2904 and milling at an angle toprevent the accumulation of redeposited material at the sides of thenotched structure being formed in the P1 pole 2904.

As the ion milling 3502 proceeds to remove P1 material 2904, the stepstructure 3504 (FIG. 35) is gradually consumed. This results in a P1structure that has a notch 3602 formed with a steep shoulder 3604, andwhich may also include a vertical notch portion 3606. The steep shouldermay taper off slightly to a more gradual slope at locations 3608 furtherlaterally outward. The steep shoulder preferably defines an angle 3610of 30-60 degrees or about 45 degrees with respect to the planes definedby the deposited layer (horizontal in FIGS. 29-36). The vertical portion3606 of the notch 3602 may extend to a depth D of about 0 to 10 nm.After forming the notched pole structure, a non-magnetic fill layer suchas alumina (not shown) can be deposited to encapsulate the pole.

With reference now to FIG. 37, the method for constructing a steepshouldered notched pole structure as described in FIGS. 29-36 can besummarized as follows. In a step 3702 a substrate is provided. Thesubstrate can be, for example a planarized alumina underlayer. Then, ina step 3704, a layer of magnetic first pole (P1) material is deposited.This material can be for example NiFe, CoFe or some other suitablematerial. In a step, 3706 a layer of write gap material, such asalumina, is deposited. Then, in a step 3708 a magnetic P2 seed layer isdeposited. In a step 3710 a RIEable film is deposited. The RIEable filmcan be, for example, SiO₂, SiN, Si, Ta, Ta₂O₅, DLC Tungsten, DURIMIDE®,etc. Then, in a step 3712 a PMGI layer (Polymethylglutarimide) isdeposited.

In a step 3714 a thick layer of deep ultraviolet (deep UV) photoresistis deposited (spun on). In a step 3716 the deep UV photoresist isphotolithographically patterned and developed to form a trench in thephotoresist layer and an undercut in the PMGI layer. Then, in a step3718 a 1^(st) reactive ion etch (RIE) is performed. This 1^(st) RIEremoves the RIEable layer within the trench to expose the P2 seed layer.In a step 3720 a magnetic material such as NiFe, CoFe or some othersuitable material is electroplated into the trench and undercut toprovide a P2 structure.

In a step 3722, the deep UV photoresist is stripped, such as by achemical liftoff process. Then, in a step 3724, a second reactive ionetch (2^(nd) RIE) is performed to from a P2 structure with wingstructures at the bottom. In a step 3726, an ion mill is performed toremove P2 seed material, write gap material and P1 magnetic polematerial to form a notched P1 pole structure. The presence of the wingson the P2 structure causes the ion mill to form a desired steepshouldered notch structure on the P1 pole notch.

While various embodiments have been described, it should be understoodthat they have been presented by way of example only, and notlimitation. Other embodiments falling within the scope of the inventionmay also become apparent to those skilled in the art. Thus, the breadthand scope of the invention should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

1. A method for constructing a wrap around trailing magnetic shield in aperpendicular magnetic write head, the method comprising: providing asubstrate; depositing a write pole material layer on the substrate;forming a mask structure over the write pole material, the maskstructure including a hard mask; performing an ion mill to removeportions of the write pole material not covered by the mask structure todefine a write pole; depositing a first layer of non-magnetic gapmaterial; performing a reactive ion mill to remove the first layer ofnon-magnetic gap material from areas over the write pole; depositing asecond layer of non-magnetic gap material; and depositing a magneticmaterial to form a wrap around magnetic shield, wherein the depositing amagnetic material to form a wrap around magnetic shield furthercomprises sputter depositing an electrically conductive seed layer, andelectroplating an electrically conductive magnetic material.
 2. A methodas in claim 1, further comprising, after performing a reactive ion millto remove non-magnetic write gap material from areas over the write poleand prior to depositing a magnetic material to form a wrap aroundmagnetic shield, performing a reactive ion etch to remove any remainingmask material.
 3. A method as in claim 1, wherein the depositing amagnetic material to form a wrap around magnetic shield furthercomprises electroplating NiFe.
 4. A method as in claim 1 wherein thefirst and second non-magnetic gap materials comprise alumina.
 5. Amethod as in claim 1 wherein the first non-magnetic gap materialcomprises alumina.
 6. A method as in claim 1 wherein the secondnon-magnetic gap material comprises alumina.
 7. A method as in claim 1wherein the ion mill performed to remove portions of the write polematerial not covered by the mask is performed at an angle with respectto a normal to the surfaces of the deposited layers in order to form awrite pole having a substantially trapezoidal shape.
 8. A method as inclaim 1 wherein the hard mask layer comprises a layer of alumina andlayer of diamond like carbon (DLC) deposited over the layer of alumina.9. A method as in claim 1, wherein the first and layers of non-magneticmaterial are deposited by a conformal deposition method.
 10. A method asin claim 1, wherein the first and second layers of non-magnetic gapmaterial comprise alumina deposited by a conformal deposition method.11. A method as in claim 1, wherein the first and second layers ofnon-magnetic gap material comprise alumina deposited by chemical vapordeposition (CVD).
 12. A method as in claim 1, wherein the first andsecond layers of non-magnetic gap material comprise alumina deposited byatomic layer deposition (ALD).